Is bacterial luminescence response to low-dose radiation associated with mutagenicity?

Luminous marine bacteria are widely used in bioassays with luminescence intensity being a physiological parameter tested. The purpose of the study was to determine whether bacterial genetic alteration is responsible for bioluminescence kinetics change under low-dose radiation exposure. The alpha-emitting radionuclide 241Am and beta-emitting radionuclide 3H were used as the sources of low-dose ionizing radiation. Changes of bioluminescence kinetics of Photobacterium phosphoreum in solutions of 241Am(NO3)3, 7 kBq/L, and tritiated water, 100 MBq/L, were studied; bioluminescence kinetics stages (absence of effect, activation, and inhibition) were determined. Bacterial suspension was sampled at different stages of the bioluminescent kinetics; the doses accumulated by the samples were close or a little higher than a tentative limit of a low-dose interval: 0.10 and 0.85 Gy for 241Am, or 0.11 and 0.18 Gy for 3H. Sequence analysis of the 16S ribosomal RNA gene did not reveal a mutagenic effect of low-dose alpha and beta radiation in the bacterial samples. Previous results on bacterial DNA exposed to low-dose gamma radiation (0.25 Gy) were analyzed and compared to those for alpha and beta irradiation. It is concluded that bioluminescence activation and/or inhibition under the applied conditions of low-dose alpha, beta and gamma radioactive exposure is not associated with DNA mutations in the gene sequences tested.